1. Field of the Invention
This invention pertains to apparatus for treating photochemicals, and more particularly to apparatus for preventing spent photo chemicals from clogging drains.
2. Description of the Prior Art
The chemistry associated with x-ray photography is well known. When a film coated with a silver emulsion, usually in the form of a silver halide, is exposed to light energy, the exposed portion of the emulsion is converted to metallic silver. The film is "developed" by treating it with an alkaline solution which makes the metallic silver more visible. Thereafter, a "fixer" is applied to the film which dissolves and carries away the silver emulsion not converted to metallic silver. Accordingly, the spent fixer solution, which is normally of an acidic nature, contains significant quantities of silver.
It is a common practice to recover the silver in the fixer solution by replacing the silver ions with iron in known chemical reactions. After being desilvered by an iron-for-silver exchange, the fixer solution is usually an opaque reddish milky liquid. The iron in the solution is in the form of ferrous oxide, and it may be present as a colloidal dispersion. Conventionally, the desilvered fixer solution is flushed down a drain. If an alkaline substance is present, the iron will precipitate in the drain. As a result, the drain frequently becomes clogged, which is a serious problem and can result in flooding an x-ray processing area. To avoid drain clogging, the acidic desilvered fixer solution and the alkaline spent developer solution may be flushed down separate drains. Since duplicate drains are expensive and are not always available, the practice of flushing the fixer with copious quantities of water is also commonly employed, thereby flushing away the iron oxides before they can form deposits in the drain. That practice is wasteful of water and often merely delays the clogging problem rather than eliminating it. Other practices to avoid drain clogging include periodic treatment of the drain with an acid type drain cleaner. That procedure, too, does not address the cause of the problem but merely treats the result.
Thus, a need exists for preventing desilvered fixer solution from clogging a drain when exposed to an alkaline developer solution.